Re: Pipewire hard disk usage (presumably) - Linux-audio-user

13 Dec 2024

Hi Chris, 
thank you for your answer!

...
   I didn't
have these problems under jack2, but then the RME was also
 connected to the Scarlett via TOSLink, so there was only one interface
 visible to the system.  
 That is the difference. When you have two interfaces either they must have the 
 sample clocks synchronized using hardware (e.g. word clock connection between 
 the devices, or possibly Toslink if the device can be configured that way), or 
 you must use software resampling.
 Errors during the software resampling is likely the cause of the noises you 
 hear.  
That's a good point. I now use the RME as the clock master, the Scarlett is connected
via TOSLink only for syncronisation and an Octo PRE 8 is connected via Wordclock BNC from
Scarlett. 
But does Pipewire somehow knows that the two interfaces (RME and Scarlett) are
synchronized and there is no need for resampling?

...

  I therefore suspect that it is a problem with
the
 hard disk usage, as I can't think of any other reason.  
 That is the least likely problem. Pipewire does not use the hard disk, and if 
 there were a problem with hard disk access by the audio application it would 
 result in underrun warnings.

  not found a way to optimize hard disk access and
I don't even know if this
 is done directly by Pipewire or if one of the usual libraries is used for
 this.  
 Pipewire does not access the hardisk so not related at all to pipewire 
 libraries.  
I admit, this was a stupid idea. I was thinking about too many disk interrupts which may
disturb interrupts for the soundcards.
But the first is of course completely out of control if pipewire.
Changing the number of processors which does the disk io in Mixbus nearly solved the
problems and the latest update of Mixbus let it completely disappear.

...

  Have you seen this phenomenon before or do you
have any ideas what
 else I can try?   
 How have you configured the two devices in Pipewire?   
Both are configured as pro_audio cards. Sample rate is 48k and buffersize is 1024
samples.

...

 Are you using the pipewire-jack interface to access the pipewire server as a 
 JACK server? If so you could try configuring pipewire so that only the RME is 
 accessed by pipewire, the Scarlett is ignored by pipewire, and then use 
 zita_a2j and zita_j2a to access the Scarlett as a resampled device.  
Yes, I use the pipewire jack libraries. Resampling hopefully is not needed anymore.

...
  Was there some reason you did not leave the Scarlett
connected using Toslink?   
Yes, if I do mixing / recording stuff I do have 2 more channels and I do not need to
switch on the Focusrite if I don't do mixing stuff. RME and my monitors are enogh if I
only want to listen to music..

Thanks for your suggestions
Holger

--  
Holger Dehnhardt
holger(a)dehnhardt.org
https://www.dehnhardt.org

--  
Holger Dehnhardt
holger(a)dehnhardt.org
https://www.dehnhardt.org